The Department for Transport has not modelled changes in car sharing rates. However, research was published by DFT in 2005 “Smarter Choice—Changing the way we travel” (Cairns S, Stoman L, Newson C, Anable J, Kirkbride A and Goodwin P; 2004). This research analysed the potential impact of car sharing on commuting vehicle trips and vehicle mileage. The report is available at:
http://dft.gov.uk/pgr/sustainable/smarterchoices/ctwwt/